452 INTERNAL SECRETIONS 



experiments of Pezard the male plumage did not appear unti 

 about four months after castration at the first moulting. 

 Evidently the female plumage had already been fixed, and a 

 change could only take place when new feathers started growing 

 during the m.oult. If the castrated hen dies before moulting 

 no change in the plumage is observed after castration (Pezard, 

 1918, p. 139). If castration is done during moulting, as in 

 some experiments of Goodale's, the feathers may show in 

 colour, in pattern, and even in shape a mixture of male and 

 female, *'the area occupied by each depending upon the age 

 of the feather germs; the younger the feather the larger the 

 area of male characters" {Goodale, 1916, p. 31). Similar 

 observations have been made by Morgan (1919) and Zawa- 

 dowsky (1922) and recently by Pezard (see p. 408). No better 

 evidence could be given in support of our assumption that 

 reaction to experimental interference depends on age. The 

 castration experiments made by myself and Bormann (1922) on 

 guinea pigs and rabbits may also be mentioned here. As 

 already shown in Chapter II., the change observable after 

 castration on the penis and its accessory apparatus depends 

 largely upon the age at which the gland was removed. By 

 varying the time of castration different degrees of development 

 of those sex characters which depend upon sex hormones may 

 be obtained. I have shown the same for the seminal vesicles 

 in the guinea pig (see pp. 20 ff.). 



It is even possible that the fixation of the sex characters 

 under the influence of the sexual hormones is a latent one, being 

 invisible at the time of the operative interference, but becoming 

 revealed in course of time. This may be the true explanation, 

 for instance, of the sexual instincts so often present in some 

 degree in castrated mammals and birds, and of the gro^vth of 

 the penis in the castrated guinea pig (see Chapter 11. ). 



Lillies statement (1923), that masculinization of the female 

 partner in twin cattle is never a complete one even when the 

 fusion of the membranes occurs very early, seems contrary to 

 our assumption. In the case of the freemartin it is, indeed, 

 very difficult to explain the resistance of the female somatic 

 cells to masculinization by assuming a fixation of characters 

 caused by the influence of female hormones acting at an earlier 

 stage. But we must not forget that possibly the antagonism 

 between the male and female gonads might be responsible. '^ 



